Filter element having at least one mat-type or sheet-type filter web

ABSTRACT

A filter element is disclosed having at least one mat-type or sheet-type filter web ( 3 ), which forms by its outside ( 5 ) at least in part a filter jacket ( 7 ) that is closed on the peripheral side, wherein along the outside ( 5 ) of the filter jacket ( 7 ) a surface configuration or modification takes place in such a manner that structures ( 11 ) that are delimited from the remaining surface ( 9 ) of the filter web ( 3 ), are joined to the filter jacket ( 7 ) and are of presentable contour and/or thickness are created, wherein the structures ( 11 ) are generated by spray-fibre application and shaping, in such a manner that in time sequence, first the structures ( 11 ) and then the filter jacket ( 7 ), or in reverse order in time sequence, first the filter jacket ( 7 ) and then the structures ( 11 ), or that simultaneously both the filter jacket ( 7 ) and the structures ( 11 ) are formed in negative or positive shape on the filter jacket ( 7 ). In addition, the production of the filter element and also a shaping device used in this production process are disclosed.

The invention relates to a filter element having at least one mat-typeor sheet-type filter web which forms with its outside at least in part aperipherally enclosing filter jacket, wherein along the outside of thefilter jacket a surface configuration or modification takes place insuch a manner that structures delimited from the remaining surface ofthe filter web are joined to the filter jacket and are formed with aprescribable contour and/or thickness.

Filter elements for filtration of gaseous and liquid fluids are readilyavailable on the market in a variety of embodiments. These filterelements, inserted into a filter housing, are used to clean suppliedfluid that is laden with dirt particles, for example in the form of ahydraulic medium, by using a mat-type or sheet-type filter web and toreturn the fluid thus cleaned from the filter housing to the fluidcircuit, in particular to a hydraulic circuit. In principle, theoperational reliability of such hydraulic circuits and of the componentsincluded therein depends largely on the proper composition of thepertinent fluids circulated therein. Especially in higher-grade systemsit is therefore necessary for economic reasons to provide suitablefilter devices for the media and fluids under consideration, in order tobe able to reliably remove impurities which occur in operation. In thecase of the filter elements mentioned, it is generally known how toassemble mat-type or sheet-type filter webs from different filtermaterials and to fold or pleat at least part of the surface areasthereof, in order to produce folded or pleated filter mats therefrom,which are placed in particular around a support tube provided withpassages. In order to protect them from damage, such filter elements areprovided on their outer periphery with suitable protective devices, suchas a fine wire mesh that follows, in particular, the folding pattern ofthe filter mat. In lieu of finely woven wire mesh it is also known toplace fiber structures, such as fabric bands around the outer peripheryof such a filter element, in order to thereby obtain protection againstdamage to the mat-type or sheet-type folded or pleated filter mats.Joining of the filter mat to the aforementioned wire mesh or even tofabric bands is elaborate and expensive, and does not guarantee in everycase that the filter mat is protected from mechanical damage. Suchadditionally applied protective devices also tend to become detached orto delaminate, in particular when the direction of fluid inflow at theaforementioned filter element reverses, for example in the case of abackwash process. The known protective devices, such as the wire meshmentioned or textile fiber structures, such as bands, furthermore havethe shortcoming that the flow and filtration characteristics thereof, ascompared to sensitive filter materials made of polyester, fiberglass orpaper web, are very different and sometimes inferior. Such protectivedevices generally do not provide any defined pre-filtering effect tospeak of.

DE 10 2005 014 360 A1 shows and describes a filter element having afilter material that is folded in a star shape and has individual filterfolds, at least one fluid-permeable support means extending at leastpartially in the space between two adjacent filter folds, at the inneror outer periphery relative to the filter folds. The support means isprovided in particular with filter-active substances or is itselfcomposed of these filter-active substances and can be used as afiltering aid. The fluid-permeable support means has, in particular, abasic structure in the fashion of a support tube that surrounds thefilter material of the filter element on the inner or outer peripherythereof. Embedded into the basic structure are filtering aids, such asbentonites, perlites, activated carbon, diatomaceous earth, and thelike, which, as filter-active substances, are capable of preventing thefilter element from becoming clogged with sludge, in that components inthe fluid that are harmful to the fluid or to system elements arereliably separated.

WO 01/37969 shows and describes a fixing band, in particular in the formof an adhesive tape, that can be placed around a pleated filter mediumin order to thus stabilize and fix individual filter folds of thepleated filter medium at their prescribable spacing relative to oneanother. This ensures that a predefined filter surface of the filtermedium is durably provided. However, pre-filtration is not possible withthis known solution.

These known filter elements are characterized in particular in that anyfunctionality imparted thereto is realized by means of a manufacturingor work step using individual components that is not optimal in terms ofits production time or material consumption.

From DE 693 16 647 T2, a filter element is known that has a porous,thick-walled, integral, self-supporting resin-impregnated andresin-bonded fibrous, tubular filter structure, having:

-   -   a hollow core;    -   an inner shell made of a first large-pore porous medium adjacent        to the hollow core; and    -   an outer shell made of a second small-pore porous medium, finer        than the first porous medium and adjacent to the inner shell,        the first and second porous media being resin-impregnated and        resin-bonded, and fluid to be filtered in operation flowing        radially inward through the tubular filter structure.

In order to improve the quality grade of this known filter element, anincrementally graded porosity is provided, in such a manner that thepores are most numerous on the outside of the filter element, thedimensions thereof being at their smallest there. Preferably, provisionsare made to incorporate on the outside of the filter element, and thusin the outer filter jacket, depressions, as structures that thenconstitute along the longitudinal axis of the filter element individualrings extending parallel to one another.

For the manufacture of the known filter element, a fibrous material ismixed with water or with another suitable dispersant, to form a slurry.Then, one or more perforated molded bodies or dies are immersed in theslurry in a felting tank containing an aqueous fiber dispersion, and byapplying a vacuum to the interior of the molded bodies the fibers arecaused to simultaneously and evenly “grow” on the molded bodies, inorder to create in this manner the structured outer contour of thefilter jacket, the known ring-shaped structures appearing as depressionsin the filter jacket and, hence, in negative form, such that because ofthe already uniform density pattern of the structures, imparting aspecial functionality is not possible.

Since it takes a relatively long time until an appropriate fiber volumegrows via the slurry process, and the slurry process can generally onlybe implemented in an elaborate manner, the object of the presentinvention, proceeding from this prior art, is to improve the prior artin such a manner that an optimal filter manufacture is made possible, inparticular in terms of the manufacturing time and material consumption,and that the filter functionality can largely be readily influenced,while maintaining the advantages of the known solution, such as forexample a high filter stability and filter quality.

This object is met according to the invention by a filter element havingthe features of claim 1 in its entirety, and by a molding tool accordingto claim 20 and a process according to claim 25.

Owing to the fact that, according to the characterizing part of claim 1,the structures are generated by means of sprayed-fiber application andmolding in such a manner that in a time sequence where first thestructures and then the filter jacket, or in a reverse time sequencewhere first the filter jacket and then the structures, or where both thefilter jacket and the structures simultaneously, are formed in negativeor positive shape on the filter jacket, a simplified manufacture of thefilter element according to the invention is achieved in acost-effective manner, compared to the slurry process described abovefor forming the structures.

Owing to the sprayed-fiber application by means of a suitable nozzleapplicator device and said molding, it is possible to effect at least onthe outside of the filter element that is composed of a mat-type orsheet-type filter web or of a plurality of such webs, a surfaceconfiguration or modification in such a manner that structures of avarying, prescribable contour and/or density are formed on the filterweb that are spatially delimited from the remaining surface of thefilter jacket, such that the outside is provided with a structuring inthe sense of a functional surface that permits differentfunctionalities, including but not limited to regions of increasedstrength, regions having embedded filtering, regions having differentfluid-routing properties, or regions having specific appearanceproperties. Owing to the targeted incorporation of fiber material bymeans of a spray application process into the respective prepared moldsurface, a molding process is created in which, in contrast to the knownslurry process, the application of the fibers into the form can becontrolled in a targeted manner, such that a very broad range ofdifferent filter elements can be produced that differ in theirfunctionality. It is provided, in this context, to either first createas a depression the outer filter jacket by means of the sprayed-fiberapplication process in the mold and then, subsequently, the respectivenegative inside structure, which process may also be reversed in timesequence, depending on the design of the production mold, in such amanner that first the positive, projecting structure is formed and thensubsequently the outer filter jacket. The delimitation between thefilter jacket and structure consists in that the filter jacket basicallyoccupies a larger or at least the same surface area as the respectivestructure to be formed in raised or recessed shape. When a plurality ofspray nozzles of the molding tool is used for the fiber application, itis also possible for the structure and fiber material to be generatedsimultaneously at least in some regions thereof.

In a particularly advantageous embodiment of the filter element, thestructures of prescribable contour and/or density arranged on theoutside of the filter jacket are designed such that the structures arecapable of determining or influencing at least to some degree the inflowor flow of the fluid through the filter element, in particular throughthe filter jacket, in the fashion of flow directing elements. Thestructures of prescribable contour are thus capable of exertingsignificant influence on the nature of the fluid flow at the filterelement, to the effect that a flow direction and velocity of the fluidflow desired by the design and also the basic nature of the flow aroundand through the filter element—turbulent or laminar—can be set. Inparticular when the structures have an increased density compared to theremaining density of the mat-type or sheet-type filter web, they can beused at least to some degree for stiffening the filter jacket. Thiseliminates in particular the need to incorporate or arrange additionalstiffening elements on the filter jacket for the purpose of increasing,for example, the dent resistance of the filter jacket.

It may also be advantageous to use the structures of prescribablecontour and/or density on the outside of the filter web for creatingpictorial, in particular numeric or alphanumeric elements, such astrademarks and the like. The structures may be depressions or raisedareas that depict a trademark for the filter element, and thedepressions or raised areas may form surfaces or lines for subsequentprinting on the structures. It is expedient to design the structures ofprescribable contour and/or density in particular for stiffeningpurposes of the filter element or also for fluid routing purposes on theoutside of the filter web in a linear or stripe shape. These linear orstripe-like structures may extend tangentially over the outside of thefilter jacket or may extend in a substantially axial direction relativeto the filter jacket. It may also be advantageous to orient the linearor stripe-like structures, at least predominantly, in the radialdirection of the filter element on the outside of the filter web. Thelinear or stripe-like structures which, as mentioned, may extendradially and/or tangentially and/or axially, can also have breaks in thecontour or orientation thereof. In a particularly preferred embodimentof the filter element, the linear or stripe-like structures have aspacing relative to each other on the outside of the filter jacket thatis chosen to be constant.

It is understood that, in particular for the depiction of pictorialsymbols by means of the linear or stripe-like structures, the same mayalso intersect. However, it may be advantageous to design the linear orstripe-like structures to be curved in an S-shaped or to have a jaggedshape. In principle, any other geometric design of the horizontalsection or cross section or longitudinal section of the structures ispossible, such that it may be advantageous to design the structures tobe disk-shaped or circular and to design them in particular asdisk-shaped or circular raised areas or depressions on the surface ofthe filter jacket. The outside of the filter jacket can be either theinflow or the outflow side of the filter element. Preferably, thestructures of prescribable contour and/or density are an integral partof the filter web and of the outside of the filter web; however, it maybe also preferable to design the structures partially or completely asaffixed components of the filter web.

In order to minimize the manufacturing effort and expense for the filterelement, it is advantageous in each case to form the structures ofindividual fibers of which preferably also the filter web is formed, atleast in part. It is understood that in addition to the filter webformed in this manner, one or a plurality of additional filter layerswith or without supporting lattices or other support means may form thefilter element, depending on the purpose of the filter element, suchthat altogether a multi-layered design of the filter element may beobtained. In particular, this makes possible through a predefined anddesired design (parameterization), an adjustment of the filtration ofthe fluid when flowing through the filter element with respect to filterfineness, direction of flow through the filter element and effect offilter aids on the fluid to be filtered.

In a particularly preferred embodiment, the filter element, with thefilter web and optional additional filter layers and support lattices,is placed around a fluid-permeable support tube in the fashion of acylindrical hollow element, such that a one-piece filter element isformed in this manner as a replaceable part for a filter housing in ahydraulic system. All of the components of the filter element mentionedso far, in particular the filter web according to the invention, may befixed between two end caps of the hollow element, such that a tradableassembly or tradable assemblies having differing structures ofprescribable contour and/or density on the surface of a filter jacketcan be created.

In order to minimize the manufacturing and in particular theinstallation time and expense for a filter element provided with thestructures according to the invention, a molding tool for manufacturingthe filter element is proposed, comprising a mold, the mold surface ofwhich has the delimited structures, but has at least the spatialdelimitation of the structures, for the filter jacket of the filterelement in the fashion of a positive or negative matrix. The moldsurface designed in such a manner is thus capable of receiving theoutside of the filter jacket in the sense of a negative-shape orpositive-shape design moldable therefrom. It is advantageous, inparticular in the case of a complex overall shape of the filter element,to form the mold of at least two identically sized mold halves, the moldhalves when assembled defining, at least partially, the delimitedstructures for the surface of the filter web. For manufacturing a filterelement in tubular shape, it is thus also advantageous to design themold to be tubular and to arrange on the inside of the mold, inparticularly exclusively on the surface of the inside of the mold, therespective matrix for creating the delimited structures of prescribablecontour and/or density for the filter web.

A mold designed in this manner, having a free space or a preferablycylindrical hollow space defined by the mold, is particularly suitablefor applying on the inside thereof with the aid of a nozzle devicehaving spinnerets, from which a plastic melt can be formed intoindividual fibers or filaments, a spun-bonded nonwoven that forms thesurface of the filter web and substantially forms the filter web itself.The nozzle device can be formed, for example in the case of asubstantially cylindrical mold, as a spraying pipe or nozzle bar havinga series of spinnerets at predefined distances from one another in axialor radial direction. In this way, and assuming that the surface of themold has self-releasing properties with respect to the applied fibers, aseamless layer or a seamless filter jacket can be created by means ofcontinuous fiber application in axial and/or radial direction relativeto the mold.

Owing to the adjustable fiber thickness, the fibers are very thin andtherefore suited to permit a multi-layer continuous application offibers or filaments created from a plastic melt (thermoplastic). Thefibers or filaments that are applied while in a plastic state settle onthe inside of the mold and on the mold components arranged therein inthe fashion of a negative matrix for creating the delimited structuresof prescribable contour and/or density for the filter web, the delimitedstructures—following a cooling and/or curing process—being permanentlymolded on the surface of the filter web. The nozzle device used for thispurpose enables in particular the amount of fibers or filaments to belocally applied via the inside of the mold, and therefore also thedesired adjustment of the density of the filter web, to be chosen inparticular in the region of the delimited structures. It is understoodthat regions of differing strength and/or regions of differing filterfineness can be created in this manner along the entire filter web.Altogether, the process according to the invention can be used to createin a simple manner a layer thickness of the filter web material formingthe surface of the filter element, which can be specified within desiredlimits.

It may be advantageous to choose a layer thickness between approximately2 mm and 6 mm. In order to be able to use the filter web producedaccording to the invention in particular as a pre-filter for the filterelement, it is advantageous to vary the filter thickness or the fiberdensity of the fibers or filaments applied to the inside of the mold inthe proposed manner over the thickness of the filter web as well. Thus,it is possible, for example, to choose the fiber density on the inflowside of the filter web to be lower than on the outflow side of thefilter web. In this proposed manner it is possible to form altogether aone-piece filter web that by itself forms a filter element. Aftercooling and solidification of the fibers or filaments in the mold, thefilter element can be removed from the mold in particular by releasingthe two or a plurality of mold elements, and reusing same for a renewedproduction process of a filter element according to the invention. Itwill be understood that the mold will need to be cleaned and/or thesurface thereof will need to be treated with a release agent prior toapplying a new filter web in the mold.

The process according to the invention for producing the delimitedstructures of prescribable contour and/or density and of the filterjacket can be used for creating filter elements that do not require anyfurther finishing, in particular no finishing of the edge seam.

The invention is shown in more detail below with reference to thedrawing. In a schematic drawing that is not to scale,

FIG. 1 shows a perspective view of the filter element according to theinvention with a fiber jacket;

FIG. 2 shows a perspective view of a molding tool for producing a filterelement comparable to the solution according to FIG. 1;

FIG. 3 a shows a perspective view of a mold half of a mold for producinga further embodiment of a filter element;

FIG. 3 b shows a perspective view of a mold consisting of two moldhalves like the one shown in FIG. 3 a;

FIG. 4 a shows a perspective view of a further embodiment of a mold halffor producing a filter element;

FIG. 4 b shows a perspective view of a mold formed of two identicallysized mold halves like the one shown in FIG. 4 a; and

FIGS. 5 to 8 show further embodiments relating to a perspective view ofa mold half for producing filter elements of different designs.

FIG. 1 shows, in a schematic perspective view, a filter element 1 as itis used, for example, in suction filters or line filters for deepfiltration of a gaseous or liquid fluid. The filter element 1 isdesigned to be hollow cylindrical with approximately uniform outside andinside diameters over the axial length thereof. The filter element 1 iscreated in a spray application process (SpunSpray process) of fibersthat are applied with the aid of a process shown in FIG. 2 of applying aplastic melt by means of a nozzle device 39 onto an inside 41 of a mold29. The filter 1 is thus formed as a one-piece component created bycontinuous application of individual fibers 23 onto a mold surface 31 ofthe mold 29. The individual fibers are applied in randomized or regulararrangement relative to one another over the thickness of the entirefilter element. The filter element 1 has a filter web 3 that is formedin the stated manner as a fiber mat of individual fibers 23 and theoutside 5 of which forms in the embodiment shown in FIG. 1 the inflowside 22 of the filter element 1, for fluid to be cleaned. The filter web3 forms a filter jacket 7 that is closed around its periphery andextends around the entire filter element 1.

As is also shown in FIG. 1, the filter element 1 is built up by layeringaltogether three filter layers 25, of which the filter web 3 forms theoutermost filter layer. The individual filter layers 25 have, in theembodiment shown in FIG. 1, a layer thickness S of approximately 2 mm to4 mm in each case. A surface 9 of the filter web 3 shows, arranged aboutthe periphery of the filter web 3, a delimited positive, projectingstructure 11 formed as a pictorial symbol 15. The pictorial symbol 15 ordelimited structure 11 is placed along the entire axial length of thefilter element 1 at predefined distances a from one another. The filterweb 3 and the pictorial symbols 15 are produced from the same material,namely a thermoplastic, such as polyamide, polypropylene, polyacrylic,or the like and are produced in a single process step. The density ofthe chosen fiber material basically does not differ within the pictorialsymbol 15 and within the filter web 3. The pictorial symbol 15 ordelimited structure has a greater geodetic height than the remainingoutside 5 of the filter web 3. This allows the pictorial symbols 15 tobe provided with a color contrasting from the surface 9 of the filterweb 3 with the aid of a simple printing process. This merely requires,for example, rolling the outside 5 of the filter element 1 onto astraight, level dye holder for printing the pictorial symbols 15.

As is also shown by FIG. 1, the filter element 1 has an additional,radially further inwardly located filter layer that has a greater filterfineness than the filter web 3. The further inwardly located filterlayer 25 a is, like the radially further inwardly located filter layer25 b adjoining same, formed in a single process step together with thefilter web 3, in a so-called SpunSpray process. The individual fibers 23of the respective filter layers 25 a and 25 b lie randomized one on topof the other, like in the filter layer 25 or in the filter web 3, withthe filter layer 25 having the greatest filter fineness of all threefilter layers shown. Fluid 13, for example hydraulic oil, is routed inthe operation of the filter element 1 through fluid-routing deviceswithin a filter housing (not shown) in which the filter element 1 ishoused, to the inflow side 22 of the filter element 1 and passes throughthe filter layers 25 to 25 b, in order to exit, after passing through asupport pipe (not shown) in the interior of the filter element 1, at theoutflow side 22′ of the filter element 1 from the filter element 1 andbe returned purified to a hydraulic circuit. However, the filter element1 can also be formed of only one peripheral layer of individual fibers.

FIG. 2 shows, in an embodiment shown merely by way of example, a moldingtool 27 for producing a filter element 1 as shown in FIG. 1. Inprinciple, the molding tool 27 has two essential components, namely ahollow cylindrical mold 29 formed of two identically sized mold halves35, and the nozzle device 39. The mold halves are formed, simplified, asthick-walled cylinder halves in which, for example, a cooling device forcooling the inside 41 thereof, may be arranged. The mold halves 35 areprovided with suitable fixing means that are not shown in any detail, inorder to releasably connect them one to the other without offset, butform-locking.

The inside 41 of the mold halves 35 has self-releasing properties inrespect of the material of the filter web 3. Provided in the surface 43of the inside 41 of each mold half 35 is a negative matrix 33 in thefashion of milling grooves or other recesses, which is a mirror image ofthe pictorial symbol 15 shown in FIG. 1 on the filter web 3. In theviewing direction of FIG. 2, the matrix 33 is formed on the right by thepictorial symbols 15 in such a way that the pictorial symbols 15 in FIG.1 are mirror-image recesses 45 in the mold surface 31 or surface 43 ofthe inside 41 of each mold half 35. The matrix 33 is formed, in theviewing direction of FIG. 2 on the left, by circular disk-shapeddepressions 21, likewise in the form of recesses of identical depthextending over the entire region of the depressions 21. As shown, thetwo mold halves 35 thus form a hollow cylinder, such that a cylindricalfree space 37 is created in the radial direction between the mold halves35.

The nozzle device 39 is formed substantially by a nozzle bar 40 of apipe 49 transporting plastic melt 47. On the nozzle bar 40, spinnerets51 are arranged evenly spaced for forming the individual fibers 23. Inthe embodiment shown, the nozzle openings 53 of the spinnerets 51 createthe individual fibers 23 hydraulically by application of pressure on theplastic melt 47, and direct the fibers nearly perpendicularly onto thesurface 43 of the inside 41 in each mold half 35 for the sprayapplication. The nozzle bar 40 is moved by a servomotor device that isnot shown in any detail in the axial direction of the mold 39, arotatory movement of the nozzle bar 40 being superposed on the axialmovement, such that the individual fibers 23 are sprayed randomized ontothe surface 43.

It may be advantageous, for improved fanning of the plastic-melt streamand for transporting the individual fibers 23 to the surface 43, to usea carrier air flow.

The structures 11 and all of the filter layers 25, 25 a, 25 b, andtherefore also the filter web 3 that bears on its outside 5 thestructures 11, are thus produced in a single process step by applyingthe individual fibers 23 in the stated manner. Alternatively oradditionally, the mold may also move relative to the nozzle bar 40.

After completed application of the individual fibers 23 and formation ofthe desired filter layers, and after a setting or solidification processof the filter layers 25, 25 a and 25 b, the mold halves 35 shown can bemoved radially apart after releasing the corresponding form-lockingconnection that has a centering function, and the filter element 1 canbe removed. The filter element 1 is characterized by an adequatestiffness for its intended purpose; the additional figures showingmeasures, inter alia, for improving the stiffness of the filter element1. FIG. 3 a, for example, shows in a schematic perspective view a moldhalf 35, in the interior surface 43 of which spiral-shaped recesses 45are recessed that are provided with a low pitch and have uniformrectangular cross sections.

The recesses 45 in the fashion of lines or stripes have identical axialdistances from one another such that, as shown in FIG. 3 in a furtherperspective view of a mold 29, they form an endless circumferentialspiral shape when the mold halves 35 are joined. When a filter element 1is produced by a manufacturing process shown in FIG. 2 by applyingindividual fibers 23 in the manner described, a filter element 1 isobtained, the outside 5 of the filter web 3 of which has a surface 9that has a spiral 55 radially projecting out from the surface 9 thereof.The spiral 55 thus formed is a delimited structure 11 that is capable ofcontributing both to the radial and/or to the axial stiffening of thefilter element 1 and also to the fluid routing on the surface 9 thereof.Identical components are identified by the same reference numerals as inthe preceding figures.

The mold may also be formed in one piece, consisting, for example, of ahollow cylindrical injection mold, and the filter element is capable ofbeing removed from the mold due to its flexibility. The filter elementcan also be removed by destroying the mold.

As shown in FIGS. 4 a and 4 b, recesses 45 may also be provided in thefashion of wrap-around rectangular grooves in the surface 43 of theinside 41 of each mold half 35 of the mold 1, for producing delimitedstructures 11 on the surface 9 of a filter element 1. The recesses 45,which are shown in FIGS. 4 a and 4 b, each extend at an acute anglerelative to one another, substantially radially relative to each moldhalf 35 and intersect tangentially approximately in the center of eachinside 41 of each mold half 35, such that, as shown in FIG. 4 b, therecesses 45 in their totality form a wrap-around shape. Accordingly,when producing a filter element in the mold 29 shown in FIG. 4 b, astructure 11 having an intersecting stripe-like shape is formed on thesurface 9 of the filter web 3 of the given filter element 1. Such astructure 11 serves mainly for axial and radial stiffening of the filterelement 1.

FIG. 5 shows in a further perspective schematic view of a mold half 35for a mold for producing a filter element 1 a further possibleembodiment of the surface 43 on the inside 41 of the respective moldhalf 35. Here, even-running recesses 45 in axial direction are shownthat have a rectangular cross-section that remains uniform over theaxial length. These longitudinal webs 57 represent a negative matrix 33that forms, after molding of a filter element in the respective mold,longitudinal ribs on the surface of the filter element that are arrangedwith uniform tangential spacing about the periphery of the filterelement 1. This results, in particular, in an improved buckling andbending stiffness of the respective filter element 1. Additionally,fluid routing channels that are of rectangular shape when viewed incross section are created at the inflow side 22 of a respective filterelement 1, between the structures 11 designed as longitudinal ribs of afilter element 1 originating from the mold half or from the mold 29.Therefore, a design of the mold in the fashion shown in FIG. 5facilitates a longitudinal routing along the outside of the filter web3, of the fluid 13 flowing towards the filter element 1.

As shown in FIG. 6 in a further perspective schematic view of a moldhalf 35 of a further embodiment of a mold 29, the recesses 45 in thesurface 43 of the inside 41 of the respective mold half 35 may also havea horizontal-section shape that is curved in an S-shape. It can also beadvantageous, as shown in FIG. 7, to design the respective recesses 45to have a jagged horizontal-section shape. The embodiment of a mold half35 shown in FIG. 6 produces a surface 9 of the filter web 3 of a filterelement 1 formed therefrom that is capable of slowing the fluid 13flowing therethrough and allowing it to flow in a laminar flow patternalong the filter element 1. The direction changes 19 of the structures11 that are formed when a filter element is molded in the mold shown inFIG. 7, can contribute to producing turbulence and slowing the fluidflow at the surface 9 of the filter web 3.

FIG. 8 shows, in a further schematic perspective view, a mold half 35for a mold 29 for creating a filter element 1, the surface 43 of whichhas lined-up circular-disk-shaped recesses having a uniform depth ofrecess that remains constant over the entire surface of each recess 45.The circular-disc shaped recesses 45 have uniform axial distances a fromeach other, such that when a filter element 1 is molded in therespective mold 29, structures 11 are formed on the surface 9 of thefilter element 1 that have breaks relative to each other.Circular-disk-shaped structures of this type are preferably capable ofgenerating different pressure differentials over the entire periphery ofa filter element 1 when fluid 13 passes through the filter element.

It is understood that the embodiments of the matrix 33 shown in all ofthe figures can be designed not only as recesses 45 but also partiallyor completely in the form of raised areas projecting out from thesurface 43 of the inside 41 of each mold half 35.

During the manufacturing process of a filter element 1 in the mannershown, additional filtering aids with chemical and/or physical actionmechanisms can be integrated into the different filter layers 25, 25 aand 25 b.

1. A filter element having at least one mat-type or sheet-type filterweb (3) which forms by its outside (5) at least in part a peripherallyenclosing filter jacket (7), wherein along the outside (5) of the filterjacket (7) a surface configuration or modification takes place in such amanner that structures (11) delimited from the remaining surface (9) ofthe filter web (3) are joined to the filter jacket (7) and are formed ina prescribable contour and/or thickness, characterized in that thestructures (11) are generated by sprayed-fiber application and shapingsuch a manner that in one time sequence, first the structures (11) andthen the filter jacket (7), or in reverse time sequence, first thefilter jacket (7) and then the structures (11), or that simultaneouslyboth the filter jacket (7) and the structures (11) are formed innegative or positive shape on the filter jacket (7).
 2. The filterelement according to claim 1, characterized in that the structures (11)create, as a negative-shape design, depressions in the filter jacket (7)or, as a positive-shape design, raised areas on the filter jacket (7).3. The filter element according to claim 1, characterized in that thestructures (11) are an integral part of the filter jacket (7).
 4. Thefilter element according to claim 1, characterized in that at least onestructure (11) transitions from a depression into a raised area and viceversa, and/or that both at least one depression and one raised area arepresent spaced apart from one another in the respective filter jacket(7).
 5. The filter element according to claim 1, characterized in thatthe structures (11) of prescribable contour and/or density determine orinfluence at least to some degree the inflow and/or the flow of fluid(13) through the filter jacket (7).
 6. The filter element according toclaim 1, characterized in that the structures (11) of prescribablecontour and/or density effect at least in part the stiffening of thefilter jacket (7) in axial and/or radial direction.
 7. The filterelement according to claim 1, characterized in that the structures (11)of prescribable contour and/or density are formed at least in part bypictorial (15), in particular by numeric or alphanumeric elements. 8.The filter element according to claim 1, characterized in that thestructures (11) of prescribable contour and/or density have a linear orstripe-like shape.
 9. The filter element according to claim 1,characterized in that the linear or stripe-like structures (11) extendsubstantially tangentially or substantially axially relative to thefilter jacket (7).
 10. The filter element according to claim 1,characterized in that the linear or stripe-like structures (11) haveradially and/or tangentially and/or axially oriented breaks (17) ordirection changes (19).
 11. The filter element according to claim 1,characterized in that the linear or stripe-like structures (11) have apredefined distance (a) from one another.
 12. The filter elementaccording to claim 1, characterized in that the linear or stripe-likestructures (11) intersect at least in some areas.
 13. The filter elementaccording to claim 1, characterized in that the linear or stripe-likestructures (11) are curved in an S-shape or are jagged.
 14. The filterelement according to claim 1, characterized in that the structures (11)are disk-shaped or circular raised areas or depressions (21) on thesurface (9) of the filter jacket (7).
 15. The filter element accordingto claim 1, characterized in that the structures (11) are arranged onthe inflow (22) or outflow side (22′) of the filter element (1).
 16. Thefilter element according to claim 1, characterized in that thestructures (11) are an integral or affixed component of the filter web(3).
 17. The filter element according to claim 1, characterized in thatthe structures (11), to the extent in which they are affixed to thesurface or top side of the filter web (3) are composed of individualfibers (23) of which preferably also the filter web (3) is formed. 18.The filter element according to claim 1, characterized in that, inaddition to the filter web (3), additional filter layers (25 a, 25 b),preferably also incorporating support lattices, are present that producea multi-layered filter-element design.
 19. The filter element accordingto claim 1, characterized in that the filter web (3) along with anyadditional filter layers (25 a, 25 b) and support lattices are placed inthe fashion of a cylindrical hollow element around a support tube andthat the aforementioned components extend between two end caps in such away that a tradable component is created.
 20. A molding tool forproducing the filter element according to claim 1, characterized in thata mold (29) is present, the mold surface (31) of which has the delimitedstructures (11) for the filter jacket (7) of the filter element (1) inthe fashion of a positive and/or negative matrix (33).
 21. The moldingtool according to claim 17, characterized in that the mold (29) isformed of at least two identically sized mold halves (35) which, whenassembled, define, at least partially, the delimited structures (11) ofthe filter web (3).
 22. The molding tool according to claim 1,characterized in that the mold (29) is designed to be tubular and formson the inside (41) thereof the respective matrix (33) for forming thedelimited structures (11) of prescribable contour and/or density of thefilter web (3).
 23. The molding tool according to claim 1, characterizedin that a nozzle device (39) that creates at least the surface (9) ofthe filter web (3) is inserted in a free space (37) of the mold (29),whereby individual fibers (23) formed from a plastic melt (47) can beapplied to the inside (41) of the mold (29).
 24. The molding toolaccording to claim 1, characterized in that the nozzle device (39) isarranged on at least one spraying pipe or nozzle bar (40) that extendsaxially through the free space (37) of the mold (29).
 25. A process forproducing delimited structures (11) of prescribable contour and/ordensity with respect to the filter jacket (7) of the filter element (1)using a molding tool (27), each according to claim 1, characterized inthat at least the material forming the surface (9) of the filter web (3)is created by spray application of fibers (23) onto a mold surface (31)of a mold (29), that the fibers (23) are formed of a solid parentmaterial that has been converted to a melt (47).
 26. A process accordingto claim 22, characterized in that at least the material forming thesurface (9) of the filter web (3) is sprayed through a nozzle device(39) onto the inside (41) of the mold (29).
 27. The process according toclaim 1, characterized in that the application of fibers (23) takesplace continuously in axial and/or radial direction relative to the mold(29) through the nozzle device (39).
 28. The process according to claim1, characterized in that by means of the continuous application offibers (23) onto the mold surface (31) a prescribable layer thickness(S) of the material forming the surface (9) of the filter web (3) isgenerated.
 29. The process according to claim 1, characterized in thatthe fibers (23) are applied in a layer thickness (S) of approximately 2mm to 6 mm onto the mold surface (31).
 30. The process according toclaim 1, characterized in that the material creating the surface (9)and/or the structures (11) of the filter web (3) is chosen such that alesser or greater filter fineness than that of the filter web (3) itselfis achieved.